Friend or stranger? Can there be less than three in a group? The interactive asks learners to prove that for seven people at a party, at least three of them are either mutual friends or mutual strangers. Pupils determine the number of friends and strangers are possible for any person at the party. Using this information, they determine the minimum number of either friends or strangers.

Concepts

combinations, factorials, probability

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Additional Tags

math

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Instructional Ideas

• Use class members to act out the scenario by connecting them with either red or blue yarn
• See if learners can determine a pattern as the number at the party changes

Classroom Considerations

• Requires signing up for a free CK-12 account to access the interactive

Pros

• Displays the correct answer when users select the wrong one
• Provides hints for some of the problems

Cons

• The directions are not clear about what the outcome of the simulation should be

Common Core

HSS-CP.B.9